﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace demo2
{
    class Circle:shape
    {
        public double radius; 

        public void GetArea()
        {
            double π = 3.14;
            Console.WriteLine("请输入圆的半径：");
            string str = Console.ReadLine();
            double r = double.Parse(str);
            Console.WriteLine("圆的面积为："+(π*r*r));
        }
    }
}
